Applanation tonometry was popularized by Goldmann as an improved method of intraocular pressure determination in comparison to indentation tonometry. The principal of Goldmann's applanation tonometry is based upon the Imbert-Fick principle, which teaches that the pressure inside a liquid-filled sphere can be determined by measuring the force required to flatten a portion of the surface. It will be obvious to one knowledgeable about the art that variations in thickness of the cornea would affect the accuracy of its applanation in the Goldmann technique. Specifically, a thinner than normal cornea would applanate easier than a normal thickness cornea, thereby generating a falsely low measure of intraocular pressure. Conversely, a thicker cornea than normal would overestimate the true intraocular pressure. Since the diagnosis of glaucoma and the assessment of the adequacy of treatment is largely dependent on intraocular pressure, the accuracy of intraocular pressure measurement is of paramount importance. In order to compensate for variations in corneal thickness, prior art has used pachymetry by optical or ultrasonic means to measure corneal thickness. It is time-consuming and expensive to use a second machine (e.g. ultrasonic pachymetry) sequentially. Moreover, it was impossible to know if the portion of cornea applanated for tonometry was the portion whose thickness was measured. Finally, the determination of both applanation tonometry and corneal pachymetry required solving an equation in order to identify the true intraocular pressure. As a result, the correction of applanation tonometry for corneal thickness variables is not generally done except in research circumstances.